What Are the Advantages and Disadvantages of FHSS and DSSS


The direct sequence spread spectrum (DSSS) technology has advantages in high-reliability applications, whereas the frequency hopping spread spectrum (FHSS) technology has advantages in low-cost applications. Generally, DSSS fast transmits data in full-band mode, and allows for a higher transmission frequency in the future. The DSSS technology applies to a fixed environment or applications requiring high transmission quality. Therefore, DSSS wireless products are usually used in wireless plants, wireless hospitals, network communities, and campus networking. The FHSS technology applies to the endpoints requiring fast mobility. Because the FHSS transmission range is small, more FHSS devices than DSSS devices are required in the same transmission environment, which requires a high cost.

Other related questions:
What are advantages and disadvantages of direct forwarding and tunnel forwarding
Direct forwarding: Packets do not need to be encapsulated and decapsulated. Therefore, the forwarding efficiency is high, and it is easy for network administrators to locate faults. However, user packets may be intercepted during transmission, threatening information security. In addition, packets of service VLANs need to be transparently transmitted, which increases maintenance workload on the Layer 2 network between ACs and APs. Tunnel forwarding: Packets are encrypted using the Datagram Transport Layer Security (DTLS) protocol, which prevents attackers from intercepting packets transmitted on the network. Therefore, tunnel forwarding has a high security. The configuration is also simple because only packets of the management VLAN need to be transparently transmitted between APs and ACs. However, encrypted packets make fault location difficult. Moreover, the forwarding efficiency is lower than that in direct forwarding because data packets must be encapsulated with a CAPWAP header.

What are advantages and disadvantages of WAPI authentication
WLAN authentication and Privacy Infrastructure (WAPI) has three independent elements: STA, AP, and Authentication Service Unit (ASU), to ensure authentication security. Encryption keys are generated after negotiation. WAPI authentication uses the SMS4 algorithm and supports 802.1X authentication applying to a large-scale network. WAPI applies to scenarios requiring high security level. In WAPI authentication, the ASU server must check certificates, which requires support from STAs. Currently, a few STAs support WAPI. STA hardware needs to be upgraded to support WAPI. Software application is not widely used because of its low efficiency.

Which should I prefer to enhance reliability of S series switches, stacking or VRRP
For S series switches (except the S1700), stacking technology combines multiple stacking-capable switches into one logical switch. After switches set up a stack, upstream and downstream devices consider them as one switch. Stacking technology provides high network reliability and forwarding performance, while simplifying network management. It has the following advantages: - High reliability Member switches in a stack work in redundancy mode. Link redundancy can also be implemented between member switches through inter-device link aggregation. - High scalabilityYou can increase ports, bandwidth, and processing capacity of a stack by simply adding member switches to the stack. Member switches can join or leave the stack without affecting other member switches. New switches automatically synchronize the configuration file and system software version with the master switch. - Simplified configuration and management You can log in to a stack from any member switch to manage and configure all the member switches in a stack. In addition, complicated Layer 2 ring protection protocols or Layer 3 protection switching protocols are not required after switches set up a stack; therefore, the network configuration is simplified. Virtual Router Redundancy Protocol (VRRP) virtualizes multiple routing devices into one logical routing device and uses the IP address of the logical routing device as the default gateway address of users to implement communication with external networks. If the gateway fails, VRRP elects a new gateway to transmit data traffic, ensuring network reliability. On a multicast or broadcast LAN (for example, an Ethernet), VRRP ensures that high-reliability default links can be provided if the gateway fails. VRRP prevents network interruption caused by a single link failure without modification in configurations of the gateway or host. Select stacking or VRRP based on actual networking requirements.

What are the advantage and disadvantage of Loader compared with conventional ETL?
Compared with conventional Extract-Transform-Load (ETL), Loader has the following advantage and disadvantage: 1. Advantage: Loader uses a MapReduce-based parallel computing architecture as the underlying architecture, which delivers a faster data processing speed than ETL. 2. Disadvantage: Compared with ETL, Loader focuses more on the data import and export function of FusionInsight Hadoop and is weak in data conversion.

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